I like the dough as flaky as possible. Letting it rest for several hours gives the gluten a chance to relax and allows the butter to solidify well, so that when the dough is baked, it creates layers of flour and butter. You can make both the filling and the dough the day before. —Chef Todd Gray, co-author of The New Jewish Table

Ingredients

2cups all-purpose flour

2teaspoons salt

1cup cold unsalted butter (2 sticks)

3teaspoons vegetable shortening

1large egg yolk

1/4cup ice water

1pound russet (Idaho) potatoes, peeled and cut into quarters

2tablespoons canola oil

1/4cup diced yellow onions

1clove garlic, minced

1/2cup ricotta cheese

1/4cup grated Parmesan cheese (1 ounce)

1tablespoon chopped fresh parsley

1/8teaspoon Freshly ground black pepper

Egg wash

Instructions

Prepare the dough: Sift the flour and 1 teaspoon salt into a large bowl. Cut in the butter using two knives. Add the shortening and egg yolk, beating until blended with a hand-held electric mixer on low speed; add the water and continue beating until the dough comes together. Transfer the dough to a lightly floured work surface and knead for 2 minutes. Wrap the dough in plastic wrap and refrigerate overnight.

Prep the potatoes: Bring a large pot of salted water to boiling over high heat. Drop the potatoes into the pot and cook until fork tender—20 to 30 minutes. Drain in a colander and set aside to dry (pat dry with a kitchen towel if they don’t air-dry quickly). Put the potatoes through a food mill (or the ricing attachment on a food processor) into a large bowl. You need 2 cups; if there is more, reserve the excess for another use.

Make the filling: Heat the oil in a small saute pan over mediumlow heat. Add the onions and garlic and saute until shiny and aromatic—3 to 4 minutes. Transfer the onion mixture to the bowl with the potatoes. Add the ricotta and Parmesan cheeses, the parsley, the remaining 1 teaspoon salt, and the pepper; mix together with a wooden spoon.

Fill the knishes: Preheat the oven to 350F. Line a baking sheet with parchment paper (the paper will adhere better if you lightly spray the pan with nonstick cooking spray before laying the paper on it). Divide the dough into three equal pieces. Roll out each piece to a 6×8-inch rectangle on a lightly floured work surface. Cut each rectangle into two 3×8-inch strips. Spoon some of the filling along the center of three strips, leaving a 1-inch margin along each edge and at the ends. Brush some egg wash along the margins; lay one of the remaining strips on top of each filled strip and press together along the edges—forming a rectangular packet. Makes three 8-inch knishes.

Bake the knishes: Arrange the knishes on the prepared baking sheet. Bake until golden brown—about 20 minutes. Cut the knishes into 2-inch lengths and serve immediately.